Even Carl Icahn, a Trump special adviser and one of the president's earliest backers on Wall Street, recently told CNNMoney he's concerned the market "has run ahead of itself." Icahn is ready for a market storm, positioning his hedge fund to profit if stocks tumble.

The problem is that the Trump rally -- the Dow is up 2,400 points since the election -- is based more on expectations than fundamentals.

Investors are very excited about Trump's promises to slash taxes, roll back regulation and unleash infrastructure. Many are betting this "pro-growth" agenda will allow the American economy to escape its sluggish trajectory.

"Eventually, earnings estimates have to start rising in order to justify investor faith in faster economic growth," Nicholas Colas, chief market strategist at brokerage firm ConvergEx, wrote in a report to clients.

Some areas of the market are running hotter than others.

For instance, optimism about OPEC's production cuts have lifted the energy sector to 28.8 times projected earnings, according to FactSet. That's easily the highest among the 11 major sectors of the S&P 500 and well above the five-year average of 24.6.